Decoration by sublimation, sometimes dye-diffusion, is a generally known process. In this process, unique sublimation dyes or inks are deposited onto a transfer or release sheet or film, to provide an image on the transfer sheet or film. The transfer sheet or film is such that it will release the dyes or inks onto the surface of an object or substrate during a second step of the process, in which the dyes or inks are sublimated and released from the transfer sheet or film to the surface of the object or substrate.
In order to transfer the image from the transfer sheet or film to the object or substrate, in the second step, the dyes or inks must be subjected to a heat press process that is a combination of time, temperature, and pressure. In this second step, the sublimation dyes are transferred at the molecular level into the object substrate, by sublimation and/or liquification.
When decorations are applied around an entire perimeter of an object there are issues that arise with respect to a seam where the decoration begins and ends. In FIG. 1, there is illustrated a cylindrical object 100 and a transfer sheet 102 partially wrapped around the cylindrical object 100. The thickness of the transfer sheet 102 is exaggerated for ease of understanding. In FIG. 2, there is illustrated a circular cross section of the object 100 in the process of being wrapped by transfer sheet 102. In FIG. 3, the same circular cross section of the object 100 has the transfer sheet 102 wrapped about it to illustrate the location of the resultant seam 104.
It is difficult to minimize the seam 104 by simply using a transfer sheet with exact dimensions because, at least in part, it is impossible to reach a tolerance level of zero in the manufacture of both the object and the transfer sheet. Further, there would have to be a tolerance level of zero in the applicator mechanisms that handle and apply the transfer sheet.
Further, when the transfer sheet has a dimension such that there is an overlap of the edges of the transfer sheet, such as illustrated in FIG. 4, there can be more dye or ink transferred at the seam given the doubling of the quantity of dye and ink at or near the seam. This can result in an extra dark and/or extra wide seam, because the increased amount of dye or ink. This can be seen in FIG. 5, which is a photograph of a bottle 200 with a darker image along a seam 202. The width of the seam 202 is very wide in region 204 at the top of the bottle.
Thus, the resultant seam is nearly always, if not always, visible and provides an undesirable discontinuity in the transferred image.
It also is known that the closeness of the transfer sheet to the object affects the transfer of dyes and inks during the sublimation step. The looser the transfer sheet is held against the object, the greater the distance between the dyes or inks and the surface being decorated. The result is that the droplets of the dyes or inks then have a greater distance over which to expand, and the resultant image becomes blurry.
Referring again to FIG. 4, it can be seen that due to the overlapping end portions 102A and 102B of the transfer sheet 102, a gap 106 will exist at the edge of the overlapped end portion 102A. Thus, the transferred image can be blurry in a region adjacent or near the seam because of the greater distance between end portion 102B and the object 100.
In FIG. 6, it is illustrated how a wrinkle 110 in the transfer sheet 102 can also create a gap 112 between the transfer sheet 102 and the object 100. Such gaps also create blurry regions in the resultant image.
U.S. Pat. No. 5,308,426 notes that decoration of objects of curved, spherical or ovoidal shapes bring about certain drawbacks when positioning a paper transfer sheet. The patent states that these drawbacks essentially reside in the fact that the paper transfer sheet does not properly deform along its principal axes, this creating irregularities in the covering of the object by the paper sheet. The patent goes on to state that such irregularities are due to the fact that the paper sheet creases or crumples when it is positioned in a vacuum around the object to be decorated. Then, at the moment of sublimation, these creases are transferred onto the surface of the object, thus adversely affecting the quality of the drawing reproduced. Such adverse effects include a discontinuity of the decoration or offsetting portions of drawing with respect to one another.
U.S. Pat. No. 5,308,426 describes addressing this problem by enveloping an object in with a transfer sheet made of and air-permeable extendible material, which while deform and conform about the shape of the object.
U.S. Pat. No. 5,962,368 describes use of a heat shrinkable material for the transfer sheet, or as an envelope about an object wrapped with the transfer sheet. The heat shrinkable material is subjected to heat before the second step in order to conform the transfer sheet about the shape of the object, and to place the dyes and inks closer to the surface of the object during the sublimation step.
However, the use of such materials requires the use of special films and the like which typically are more expensive than paper transfer sheets.
The use of paper transfer sheets in particular can give rise to other issues. As noted above, paper transfer sheets are less likely to conform about the shape of an object. Further, they can give rise to greater air gap at the seam because paper is less malleable than plastic.